Intermittent fasting—or going certain windows of time without food—is all the rage, praised mostly for its anti-inflammatory and gut-healing benefits. In a recent article, Dr. William Cole discussed the potential downsides and benefits of fasting when it comes to hormonal health. And it's true, depriving yourself of food for a certain amount of time does raise concerns, especially when it comes to female hormones and reproductive health. As a board-certified obstetrician and gynecologist and the founder of the highly successful Integrative Medical Group, this is something I've been researching and studying for years. So, let's dive in to what I know to be true about fasting and female hormones:

Your body has built-in mechanisms that promote or prevent pregnancy.

Nature provided women with amazing internal mechanisms to ensure survival and promote reproductive success. When energy reserves are low because of a lack of food, a temporary (but happily reversible) inhibition of the hypothalamic-pituitary-ovarian axis––the system which regulates the rhythmic female hormones and ovulation—occurs. This is what happens in women with anorexia, for example. Nature shuts down the production of hormones so that these women don't become pregnant, which could seriously threaten the lives of both mother and baby.

These reproductive functions are regulated by a center that exists in the brain. This area of the brain, called the hypothalamus, contains specialized cellular sensors that can detect the level of energy available from food and, depending on that level, initiate processes which either create or conserve energy in the body. Studies in mice have demonstrated that there are special types of neurons in the specific reproductive areas of the hypothalamus called kisspeptin neurons. These unique neurons are clustered in two areas of the hypothalamus: one that promotes reproductive functions, including ovulation, and one that blocks these functions. These neurons also control the release of certain brain hormones called gonadotropins. Gonadotropins tell the pituitary gland to make the hormones that, in turn, tell the ovaries to make estrogen, in accordance with the amazing rhythm that the female body follows. This fabulous kisspeptin neuron system communicates with these other sections of the brain and sends signals downstream to the ovaries. In times of acute metabolism stress, this system is able to adapt rapidly so as to preserve the woman's life and delay conception for a safer time.

There's still a lot to learn about the effects of intermittent fasting on female hormones.

But where does all of this take us regarding the use of fasting, or of the fasting-mimicking diet developed at the USC School of Longevity? Is a lack of the right quantity of nutrients going have a negative impact on fertility? And how long without food is too long?

These are the questions I hope to answer decisively in the future with the support of studies and research. But based on what we know now, my prediction is that short periods of fasting will actually enhance fertility. The reason I believe this to be the most likely result is that a few days of fasting is not long enough to be perceived by the body as dangerous. However, it is long enough to produce the enormously beneficial effects we now recognize as resulting from fasting. It has been proved that the use of the fasting-mimicking diet for five days stimulates rejuvenation of the cells in the brain, along with an increase in what is called brain-derived neurotrophic factor (BDNF)—a substance that leads to improvements in mood and cognition.

Prolonged fasting is akin to starvation, but a short fast of a few days can rejuvenate the reproductive system, increase energy production, reset the circadian clock, lower inflammation, and improve the gut microbiome. More research is certainly needed, but while we await the studies, my recommendation for all women who meet the basic guidelines for fasting and are planning a pregnancy is to begin a regular fasting routine. The general information on the benefits of fasting is so positive, it is my belief that these benefits far outweigh any theoretical negatives.